Kinetics of crystallization of Ni<inf>3</inf>P phase from amorphous Ni–P powder alloy precursors for preparation of Ni<inf>3</inf>P-rich alloys

Abstract

Due to their high hardness, excellent redox ability, good corrosion resistance and catalytic abilities, the materials with high content of crystalline Ni3P phase are promising candidates for application in various fields. In this work, amorphous and amorphous/nanocrystalline Ni–P powder alloys-precursors were prepared by chemical reduction, and further subjected to crystallization process to obtain Ni3P-rich alloys. Two different Ni–P alloys-precursors (“1” and “2”) were prepared using different reactant ratios. Applying DTA and XRD techniques, the range of thermal stability and thermally induced microstructural transformations of individual Ni–P alloys (precursors of Ni3P-rich alloys) were studied. SEM analysis allowed evaluation of particle size distribution for individual Ni–P samples. Microstructure of the as-prepared and thermally treated samples and mechanism of thermally induced transformations, including the phase composition of completely crystallized material, exhibited significant dependence on the reactant ratio used in the synthesis. Kinetic triplets of individual crystallization steps were deduced by processing the DTA curves, including deconvolution of complex crystallization peaks. Although exhibiting somewhat higher Ni3P crystallization Ea than the Ni–P alloy 1, the Ni–P alloy 2, obtained by use of larger amount of the reducing agent, gave greater content of the Ni3P phase in the crystallized material, around 90% (mass). Graphical abstract: (Figure presented.)